Studies on the Effects of Pollution on the Diaton Communities of the St Lawrence River Near

Abstract

Abstract A study was conducted to establish the physico-chemical and biological characteristics of two water masses (St. Lawrence and Ottawa) just before they meet near Montreal. The two water masses show marked differences in physico-chemical properties and in the composition of algal communities they support. As compared with that of St. Lawrence River, the water of Ottawa River shows lower values of alkalinity, conductivity, total hardness and chlorides. The value of pH is also slightly lower. But the quantity of Silica and Ammonia present in the Ottawa River is much higher. There is a marked difference in the composition of Algal communities supported by the two water masses. Over 100 species of Diatoms were found to colonize the artificial substrates (glass slides), of which only about 40 species were found to be common in both waters. Some 38 species were found only in St. Lawrence River and another 39 species only in Ottawa River. The two water masses also differed in supporting other groups of algae. Cladophora glomerata was very abundant in Ottawa River, whereas, it was absent or very rare in St. Lawrence River. On the other hand, some members of Zygnemaceae (like Sirogonium sticticum, Spirogyra sp., Mougeotia sp., and Zygnema sp.) were very abundant in St. Lawrence River and very rare in Ottawa River.